Whelan, a forward, reputedly owed his advancement at junior level to the good offices of Paddy Moore's wife, who brought the youngster's potential to her husband's attention, in his capacity as manager of renowned Dublin junior schoolboy club Stella Maris. Whelan subsequently graduated from Stella Maris as a talented young player to, Home Farm, where his precocious prowess earned him a brief but ultimately fruitless trial period at Chelsea F.C.
Upon his return to Ireland, Whelan placed his talents at the disposal of St. Patricks Athletic, a club still riding the initial surge of momentum which had elevated it from junior football in 1950 to instant League of Ireland champion status in the 1951-52 season. Whelan contributed an aggregate of 89 league goals to St. Pat's scoring ledger in a ten-year tenure at Richmond Park which encompassed FAI Cup victories in 1959 and 1961 (the latter of which remains, as of 2008, St. Pat's most recent success in the competition.) Whelan attained full international status in 1963, winning the first of two Republic of Ireland caps against Austria in a European Nations Cup qualifier.
Was awarded a benefit game in May 1963 .
He scored the winner in the 2-1 defeat of an English League XI in October 1963 .
He guested for Shamrock Rovers in a benefit game in May 1965 .
The toll exacted upon Whelan's ability and availability by an accumulation of injuries contributed to his departure from St. Pat's in November 1966, whereupon he commenced a seven-year association with Drogheda United. Whelan steered Drogheda to an inaugural appearance in the 1971 FAI Cup final, where the Co. Louth club succumbed to Limerick City after a replay. It would be a further thirty-four years before Drogheda captured the blue riband event of Irish football, but Gavin Whelan's opening goal against Cork City in the 2005 decider brought his family's footballing narrative full-circle; the midfielder is Ronnie Snr.'s grandson.
Whelan signed for Córas Iompair Éireann who were then in the League of Ireland "B" division, in January 1974 and also played for Aer Lingus at Leinster Senior League level for some considerable time thereafter.
Whelan died in July 1993 at the age of 56. By this stage, his sons Ronnie Whelan Jnr. (a 53-cap Republic of Ireland international and the winner of countless trophies and plaudits with Liverpool F.C.) and Paul Whelan (at Shamrock Rovers) were both enjoying professional careers, and his grandson Gavin Whelan has also gone on to be a professional footballer.